Heretofore, many compounds having a tricyclodecane or tricycloundecane skeleton have been synthesized and are drawing attention in the fields of perfumes, insecticides and germicides.
Examples of typical insecticides which have been known for a long time are organic phosphorus insecticides, organic chlorine insecticides and carbamate insecticides.
Among these, the use of some of highly toxic organic phosphorus insecticides and organic chlorine insecticides which are likely to accumulate in the environment, is presently prohibited. Pyrethroid compounds having high safety are used in place of some of these prohibited insecticides together with lowly toxic organic phosphorus insecticides and carbamate insecticides.
Pyrethroid insecticides have advantages in that they have a wide insecticidal spectra, high insecticidal activity and rapid effectiveness, do not allow insects to exhibit resistance and are substantially not harmful to warm-blooded animals. They have, however, disadvantages in that they are unstable and have a tendency to polymerize or to be decomposed or oxidized by high temperature, moisture or light, so that they are lacking in persistence and after-effectiveness. Furthermore, they are highly poisonous to fish and expensive.
Pyrethroid compounds have been used as domestic insecticides, mainly employed indoors, for a long time because of their high safety. For example, a pyrethroid compound having relatively high volatility is used by itself in a mosquito-repellent incense or a mosquito-repellent mat. Furthermore, a pyrethroid compound exhibiting highly rapid effectiveness and one exhibiting high lethality are combined and a synergist is added thereto to prepare an aerosol. Recently, a pyrethroid compound exhibiting both high after-effectiveness and lethality and one exhibiting highly rapid effectiveness are used in combination to prepare a coating aerosol. The pyrethroid insecticides have advantages in that they have a wide insecticidal spectrum, a high insecticidal activity and rapid effectiveness, are almost harmless to warm-blooded animals, and cause insects to exhibit no resistance. They have, however, disadvantages in that they are unstable against heat, light, oxidation and moisture, generally lacking in persistence and after-effectiveness, expensive and highly poisonous to fish. Further, they have the following disadvantages in their applications. Namely, (1) an aerosol comprising a combination of a pyrethroid compound exhibiting rapid effectiveness and one exhibiting high lethality is expensive; (2) though water-based insecticides are recently drawing attention on the basis of a growing recognition that the use of oil-based aerosol insecticides are dangerous, most of the pyrethroid compounds which have been used heretofore are liable to undergo hydrolysis during storage as water-based insecticides, because they are esters of primary alcohols; and (3) when they are used outdoors for gardening, etc., satisfactory effects cannot be obtained with respect to persistence and after-effectiveness by the use of the conventional pyrethroid compounds alone.